Atoms, elements and compounds Flashcards
Explain what the formula Na2CO3 shows about the compound. (2marks)
sodium and carbon and oxygen
all correct numbers linked to correct elements
i.e. 2 atoms of sodium, a / 1 atom of carbon, 3 atoms of oxygen
Chemical equations are always balanced. Explain why. (1 mark)
no atoms are lost / made (during a chemical reaction) or
the atoms are rearranged (during a chemical reaction)
accept because of (the law of) conservation of mass / matter
Why is sodium chloride a compound? (2 mark)
two different / types atoms / elements / ions
bonded / joined together
do not accept different size
Why is titanium an element? (1 mark)
all atoms are the same / it only contains one type of atom
do not accept only got one atom
do not accept all atoms are the same size
ignore particles
An atom of argon has 18 protons and 22 neutrons. Work out its atomic number and its mass number. (1 mark)
The atomic number is 18. The atomic mass is 18 + 22 = 40.
Use ideas about electron arrangements to explain why the elements in Group 0 have similar properties. (2 marks)
The highest occupied energy level of each group 0 element contains 8 electrons. It is because there are the same number of electrons in the highest occupied energy level of each group 0 element, the group 0 elements have similar properties.
How many elements join together to make the compound sodium chloride? (1 mark)
Two – sodium and chlorine
Use ideas about atoms to explain the difference between an element and a compound. (2 marks)
An element is made up of one type of atom only. A compound consists of atoms of more than one type bonded together
Explain how sodium and chloride ions are formed when sodium chloride is made from its elements. (2 marks)
When sodium chloride forms from its elements, one electron is transferred from the outer shell of the sodium atom to the outer shell of the chlorine atom to complete that shell. This results in a sodium ion with a single positive charge, Na+, and a chloride ion with a single negative charge, Cl-.
Explain how the atoms in a carbon dioxide molecules are held together. (1 mark)
In carbon dioxide, electrons are shared between the carbon and oxygen atoms.
A molecule of sulphur trioxide consists of one atom of sulphur joined to three atoms of oxygen. Work out its formula. (1 mark)
SO3
don’t forget the 3 should be subscripted!
The formula of potassium manganate (VII) is KMnO4. Explain what the formula tells us about this compound. (2 marks)
In potassium manganate (VII) (potassium permanganate), there are four atoms of oxygen and one atom of manganese for every one atom of potassium.
